Dr. Harry Klee joined the horticultural sciences department at the University of Florida with one goal in mind: to discover why heirloom tomatoes were so much more flavorful in the past than they are today. With his new study, published in the journal Science in late January, he has done just that.
The first order of business was to uncover why tomatoes lost so much of their flavor, something that quite quickly became clear: when it comes to commercial distributors, flavor doesn’t sell — yield, disease resistance, and firmness for ease of transport do. And as breeders select for these qualities, they lose out on flavor, quite literally breeding the deliciousness out of tomatoes.
“Think of the tomato flavor as a symphony with lots of notes,” Klee told the New York Times. “Over the last 50 years, they’ve removed one instrument at a time.”
But with this new research at our fingertips, scientists may be able to add the various “notes” back to tomatoes so that they can express all of that latent yet delicious flavor.
The Flavor of Heirloom Tomatoes Boiled Down to its Essence
Discovering the delicious gene was no easy feat, at least not when it came to tomatoes, whose flavor is made up of three primary components: sugars, acids, and volatile chemicals that carry aroma. Those volatile chemicals, especially in the case of the tomato, are difficult to get a handle on.
“If we look at something like a banana or a strawberry, I can give you one chemical that you would smell, and you’d say, ‘Oh, it’s a banana,’” says Klee. “There are some very distinct flavors in those kinds of fruits that really dominate the flavor profile. In the case of the tomato, I can’t do that.”
The 25 to 30 volatile chemicals present in tomatoes are the true source of the fruit’s flavor, according to Klee, who also notes that the reason that tomatoes lose so much flavor after some time in the fridge is that the volatile chemicals are negatively impacted by the cold.
To identify these all-important volatile chemicals, Klee and his team started at the very beginning: they sequenced the whole genome of 398 modern tomatoes, then selected 160 varieties and gave them to a 100-person panel for tasting. The resulting data was then used to associate genetic variants with specific aroma and flavor traits.
With this method, researchers were able to identify 26 genes involved in producing flavorful volatiles, like a recipe for the perfect tomato.
“You can almost assemble a molecular toolkit,” says Klee. “We have identified a pathway to really significantly improve the flavor of tomatoes.”
Is it Time for the Heirloom Tomatoes of the Future?
While the research was a success, don’t expect huge, delicious heirloom tomatoes to be popping up everywhere just yet.
Firstly, the researchers weren’t looking to create a franken-tomato of the future, but rather revisit the true heirloom tomatoes of the past.
“We’re not creating anything new,” says Klee. “We’re just stepping back 50 or more years and saying here’s what you lost, and here are the genetic markers that allow you to go back to the old varieties and recover it.”
But even more than the researchers’ intentions, genetics are still standing in the way of flavorful giant heirloom tomatoes. Some traits, the team discovered, are incompatible – and size and sugar are two of them.
“Some key genes linked to sweetness are also linked to the fruit’s smaller size,” reports the Verge. “So if you want larger tomatoes, you’d probably need to give up that sweet tomato flavor.’”
No Need to Fear GMO Heirloom Tomatoes
This is not the first time that people have tried to improve tomatoes through science. The very first GMO crop to hit the American market was the Flavr Savr tomato in 1994. This variety promised to ripen more slowly, thus preventing it from rotting or becoming soft in the time it took for consumers to eat it.
While the goals of this research were different, the question does beg to be asked: will the heirloom tomatoes of the future be genetically engineered?
Not if Klee has anything to say about it.
“I don’t want people to not eat a great-tasting tomato because they’re scared of it,” he says.
While genetic engineering might be a quicker means to the perfect tomato, Klee thinks that classical breeding using molecular markers to track inheritance is a better, easier option.
“I won’t say somebody won’t use [genome editing], but honestly I think that they don’t need to use it.”
With Klee’s team’s research now readily available, the road to tastier heirloom tomatoes should be smooth sailing from now on.
“We know exactly what needs to be done to make it right,” he told the New York Times. “We just have to turn the crank.”
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